Visual Pigments of Three Species of Cartilaginous Fishes

Abstract

RETINAE were removed from dark adapted ratfish, Hydrolagus colliei; Pacific dogfish, Squalus suckleyi; and big skate, Raja binoculata, obtained by bottom trawling near Friday Harbor, Washington. Retinal extracts were prepared by a standard procedure and analysed with a Cary 14 spectrophotometer by the method of partial bleaching¹. The bleachings were with λ640 nm, λ610 nm and dim white light for six ratfish extracts; and λ660 nm, λ640 nm and λ610 nm for three dogfish and two skate extracts. For each extract of a species, a plot of the three difference spectra, expressed as δD_max=100 per cent, resulted in three congruent curves indicating the presence of a single visual pigment. In all extracts, the λ_max of the product of bleaching was 367 nm (indicative of retinene₁ oxime), so the visual pigment of each species is based on retinene₁. The λ_max of the visual pigment of each species was estimated from a nomogram² and a chart³ for determining the λ_max of visual pigments based on retinene₁. The visual pigment of the ratfish has λ_max = 484.0 nm; that of the dogfish has λ_max = 497.5 nm; and that of the skate has λ_max= 497.0 nm.